Electronics, both passive (sensors to detect control quantities) and active (actuators for directly operating mechanical components), are increasingly present in modern motor vehicles. For example, virtually all motor vehicles have electronic injection, namely fuel injectors that are operated by electric actuators piloted by an electronic control unit, and are fitted with a lambda sensor, or rather a probe able to detect the composition of the exhaust gas. Recently, the application of DBW (Drive By Wire) systems has been proposed, in which the accelerator is no longer mechanically connected to the engine throttle control, but is only connected to a position sensor that detects the position of the accelerator and, in consequence, pilots an actuator that mechanically operated the butterfly valve.
DBW (Drive By Wire) systems are provided with an electronic control unit, which receives readings from a position sensor that detects the position of the accelerator and operates an electric actuator that controls an electric drive that pilots the butterfly valve's actuator. A particularly dangerous fault that would normally impose immediate switching off of the engine (or rather the halting of the motor vehicle) is the disconnection of the cable that connects the electronic control unit to the electric drive that pilots the butterfly valve's actuator, as in this situation the electronic control unit is no longer able to control the position of the butterfly valve.